Influence of season and pollution on the antioxidant defenses of the cichlid fish acara (Geophagus brasiliensis)

The livers of Geophagus brasiliensis collected from both a nonpolluted site and a polluted site were analyzed for different antioxidant defenses, O-2 consumption, thiobarbituric acid-reactive substance (TBARS) levels, and his tological damage. Compared to controls (116.6 +/- 26.1 nmol g(-1)), TEARS l evels were enhanced at the polluted site (284.2 +/- 25.6 nmol g(-1)), as al so was oxygen consumption (86.6 +/- 11.3 and 128.5 +/- 9.8 mu mol O-2 min(- 1) g(-1), respectively). With respect to enzymatic antioxidants, increased catalase activities (8.7 +/- 1.3 and 29.2 +/- 2.4 mmol min(-1) g(-1), respe ctively), unchanged superoxide dismutase activities (767.2 +/- 113.3 and 56 3.3 +/- 70.2 U g(-1), respectively), and diminished glutathione S-transfera se activities (29.0 +/- 3.2 and 14.9 +/- 3.2 mu mol min(-1) g(-1), respecti vely) were detected. Reduced glutathione (1.91 +/- 0.17 and 1.37 +/- 0.25 m M, respectively), oxidized glutathione (1.50 +/- 0.20 and 0.73 +/- :0.17 mM , respectively), and total glutathione (3.30 +/- 0.26 and 2.07 +/- 0.27 mM, respectively) concentrations were also below control values at the pollute d site. Nevertheless, the observed ethoxyresorufin-O-deethylase activities (1.34 +/- 0.11 and 16.7 +/- 0.21 pmol min(-1) mg(-1), respectively) showed enhanced values at the polluted site. The main histological damage observed in the hepatocytes from fish collected at the polluted site was characteri zed by heavy lipid infiltration. Fish collected at the end of spring showed higher O-2 consumption, higher superoxide dismutase and glutathione S-tran sferase activities, and higher total and oxidized glutathione concentration s compared to the beginning of autumn. No seasonal changes were observed in catalase activities, glutathione or TEARS levels. Fish chronically exposed to relatively high pollution levels seem to be unable to set up adequate a ntioxidant defenses, probably due to severe injury to their hepatocytes. Th e higher antioxidant defenses found at the end of spring are probably relat ed to the enhanced activities during high temperature periods in thermo-con forming organisms.